This invention relates to fluid handbrake control systems, and while the invention is subject to a wide range of applications, a preferred embodiment of the invention will be particularly described as applied to a hydraulic handbrake control system having an improved lock control mechanism.
It is common practice in braking systems for railway vehicles to provide hydraulic brake actuators on a vehicle that can at times be responsive to service brake control apparatus, and at other times responsive to hydraulic handbrake control apparatus. Such systems can be of the type disclosed, for example, in the Engle U.S. Pat. Nos. 3,508,794, 3,622,207, 3,707,309 and 3,910,641. The merging of the service and handbrake control systems, according to these patents, requires the use of special devices known as interceptor valves to jointly govern flow of hydraulic fluid to a brake cylinder common to both systems, in order to avoid undesirable characteristics as discussed in column 1 of the above U.S. Pat. No. 3,622,207. Another Engle U.S. Pat. No. 3,910,641 discloses such a system for an articulated carrier wherein a handbrake control mechanism on one of the sections of the vehicle governs the application of handbrakes on a plurality of sections of the vehicle. All of these patents require the brake cylinders to be of the type having hydraulically operated locks for governing mechanical locking of brake actuating mechanisms.
An object of the present invention is to provide a hydraulic handbrake control system which substantially obviates one or more of the limitations and disadvantages of the described prior art systems.
Another object of the present invention is to simplify hydraulic handbrake control systems by eliminating the need for mechanical locking of brake actuating mechanisms while maintaining safe handbrake control.
Another object of the present invention is to reduce the costs of hydraulic handbrake actuating mechanisms.
Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.